Cyclotron Research Center, University of Liège, 4000 Liège, Belgium.
Proc Natl Acad Sci U S A. 2014 Apr 22;111(16):6087-91. doi: 10.1073/pnas.1320005111. Epub 2014 Mar 10.
Light is a powerful stimulant for human alertness and cognition, presumably acting through a photoreception system that heavily relies on the photopigment melanopsin. In humans, evidence for melanopsin involvement in light-driven cognitive stimulation remains indirect, due to the difficulty to selectively isolate its contribution. Therefore, a role for melanopsin in human cognitive regulation remains to be established. Here, sixteen participants underwent consecutive and identical functional MRI recordings, during which they performed a simple auditory detection task and a more difficult auditory working memory task, while continuously exposed to the same test light (515 nm). We show that the impact of test light on executive brain responses depends on the wavelength of the light to which individuals were exposed prior to each recording. Test-light impact on executive responses in widespread prefrontal areas and in the pulvinar increased when the participants had been exposed to longer (589 nm), but not shorter (461 nm), wavelength light, more than 1 h before. This wavelength-dependent impact of prior light exposure is consistent with recent theories of the light-driven melanopsin dual states. Our results emphasize the critical role of light for cognitive brain responses and are, to date, the strongest evidence in favor of a cognitive role for melanopsin, which may confer a form of "photic memory" to human cognitive brain function.
光是人类警觉性和认知的有力刺激物，可能通过一个严重依赖光色素黑素视蛋白的光感受系统起作用。在人类中，由于难以选择性地分离其贡献，因此，关于黑素视蛋白参与光驱动的认知刺激的证据仍然是间接的。因此，黑素视蛋白在人类认知调节中的作用仍有待确定。在这里，十六名参与者接受了连续且相同的功能磁共振成像记录，在此期间，他们执行了一个简单的听觉检测任务和一个更困难的听觉工作记忆任务，同时持续暴露于相同的测试光（515nm）下。我们表明，测试光对执行大脑反应的影响取决于个体在每次记录之前暴露于的光的波长。当参与者在 1 小时以上暴露于更长波长（589nm）而不是更短波长（461nm）的光下时，测试光对执行反应在广泛的前额叶区域和丘脑中的影响增加。这种先前光暴露的波长依赖性影响与最近的光驱动黑素视蛋白双态理论一致。我们的结果强调了光对认知大脑反应的关键作用，并且是迄今为止支持黑素视蛋白具有认知作用的最强证据，它可能为人类认知大脑功能赋予一种“光记忆”形式。
